The present invention relates generally to nonimpact printers, and in particular to a device for feeding constant pressure fluid to a nonimpact printing head which is arranged to scan across a writing surface.
In nonimpact printers where an ink jet printing head is reciprocally moved at high speeds to scan across a recording sheet, a pressure variation tends to occur when the head is making a turn at each end of a scanned line path due to the momentum of the liquid in a flexible conduit that is connected to the head for movement therewith.
A nonimpact printer shown and described in Japanese Pat. No. 54-10449 comprises a loop of flexible conduit which is divided into first and second half sections at a first node connected to an ink source and at a second node connected to a reciprocally movable ink jet printing head. The ink is supplied through the first and second half sections of the flexible conduit to the printer. Since the pressure variation that occurs in each of the half sections is opposite to the pressure variation that occurs in the other half section, such pressure variations could be cancelled out from each other.
However, due to the flow resistance which still exists in the inner wall of the supply conduit and in its curved path, the flow movement in the conduit tends to be converted into pressure variations. The problem becomes apparent when a quick response ink jet printing head as that disclosed in U.S. Pat. No. 3,747,120 is employed. Specifically, the pressure variation which might occur in such printing heads needs to be held below 0.033 kilograms/centimeter square for satisfactory operation. The prior art printer thus fails to meet this requirement and thus improvement has been desired.